Camera with lens protection barrier member opened/closed with uniform force

ABSTRACT

A camera has a lens protection barrier member and an opening/closing mechanism that includes a cam and a spring member, the force of which varies. The cam is designed so as to compensate for the variation of spring force and maintain a uniform operating load.

This is a division of application Ser. No. 08/418,899 filed Apr. 7,1995, which is a continuation of application Ser. No. 08/270,319 filedJul. 5, 1994 (abandoned), which is a continuation of application Ser.No. 08/138,385 filed Oct. 20, 1993 (abandoned), which is a continuationof application Ser. No. 07/717,346 filed Jun. 18, 1991 (abandoned),which is a continuation-in-part of application Ser. No. 07/607,710 filedNov. 1, 1990 (abandoned).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens driving device for a zoom or amultifocus lens housing of a camera.

2. Related Background Art

Hitherto, in order to smoothly rectilinearly move a zoom or a multifocuslens, a lens driving device has been arranged in such a manner thatthere are provided a guide member for rectilinearly guiding the lens anda supporting member for supporting the guide member, and the guidemember and the supporting member are arranged to be movable.

FIGS. 1, 2A and 2B are schematic views which respectively illustrate anexample of the above-described structure.

A roller 1 serving as the support member is placed within a groove hole2 formed in a guide member 3. Since the roller 1 is arranged to becapable of freely rotating, an excellent driving efficiency can berealized in comparison to a structure in which a pin is employed.Furthermore, the lens can be rectilinearly moved without a play or acatch even if excellent parallelism between the guiding direction andthe optical axis and the accuracy are not realized.

However, the above-described conventional structure has a problem inthat, in a case as shown in FIG. 2A in which the guide member isarranged to be a fork-like shape, the parallelism of the two sidesurfaces of the groove hole 2 in the guide member 3 which is positionedin contact with the roller 1 cannot be maintained by the side pressuregiven from the roller 1 when the lens is rectilinearly moved. As aresult, the two end portions of the fork-like guide member 3 areundesirably opened, causing the accuracy in the guiding action to bedeteriorated and a play to be generated. In order to overcome thisproblem, a structure has been employed in which the groove hole 4 is, asshown in FIG. 2B, closed. However, it leads to a fact that the lengthand the size of the guide member cannot be reduced. Therefore, theconventional technology encounters a problem in that a desire to reducethe size and the thickness of the camera for the purpose of realizing acollapsible lens housing cannot be met.

Hitherto, as light shielding means, a structure has been employed inwhich a light shielding member made of rubber, paper, or woven fabric issecured to a camera body or a lens housing at, for example, the innerhelicoid by an adhesive or the like so as to cover the gap.

As an alternative to this, a rubber washer is inserted between thecamera body and the lens housing for the purpose of covering the gap insuch a manner that it is not fixed.

The above-described light shielding structure of a type in which thelight shielding member is secured to the inner helicoid encounters aproblem in that, if there is an eccentricity generated between the innerhelicoid and the lens housing due to manufacturing or an eccentricitygenerated due to the assembling work or the adjustment work, a gap isformed due to the thus generated eccentricity, causing light to beleaked. If the light shielding member is strongly abutted against theinner helicoid for the purpose of preventing the light leakage, anexcessively large resistance arises at the time of the rectilinearmovement of the lens housing, causing a load necessary to drive the lenshousing to be excessively enlarged.

In the case where the rubber washer is inserted between the camera bodyand the lens housing in such a manner that the washer is not fixed, thelight leakage due to the above-described eccentricity can be prevented.However, a gap is formed with the inner helicoid when the lens housingis moved, in particular, when the same is forwards moved. In particular,light travelling in the direction except for the direction of theoptical axis leaks.

Furthermore, in a camera of a type arranged in such a manner that anelectric device including a CPU, a collimator and a photometer and thelike is provided in the camera housing and an electric device includinga shutter operating portion and a focusing device and the like isprovided in the lens portion, a flexible print substrate (to be calledan "FPC" hereinafter) for establishing the connection between theabove-described two electric devices is accommodated in the lens housingin a spiral or folded manner.

In the above-described conventional structure, the FPC is not insulatedfrom the inside portion of the lens housing. Therefore, the FPC has anexposure portion confronting the optical axis, causing the surface ofthe FPC to reflect the diffused light. As a result, a problem in termsof a ghost image takes place. Accordingly, coating or tape applicationbecomes necessary in order to prevent the light reflection, causing themanufacturing cost to be raised.

Furthermore, there has been a fear of introduction of the FPC deflectedinto the optical path, causing the travel of the light beam to beobstructed. If the above-described problem is prevented by a designarrangement, the FPC must forcibly be bent or deflected so as to realizethe above-described arrangement. As a result, the FPC is applied withexcessively large force, causing the durability to be deteriorated.

Hitherto, a variety of cameras each of which has a barrier have beenknown which is arranged in such a manner that the forward end of theimaging lens is selectively capped by a barrier which is arranged to beoptionally opened/closed. A barrier of the type described above iseffective to protect the imaging lens from a damage due to anundesirable contact with an external substance or an adhesion of dust orthe like. Furthermore, the above-described structure reveals anadvantage in comparison to a lens cap employed in ordinary cameras sincethe fear of missing can be prevented. Therefore, it is preferable that abarrier of the type described above be employed in compact cameras.

As a camera with a barrier of the type described above, a collapsibletype camera has been known. A collapsible type camera of the typedescribed above usually employs a barrier opening/closing mechanismcapable of automatically opening/closing the lens protection barrier insynchronization with the retraction/protraction action of the lenshousing which holds the imaging lens. The reason for this lies in thatit is advantageous in terms of operation and handling that the barrieris automatically opened/closed in synchronization with the movement ofthe lens housing since the lens housing is retracted in the camerahousing when a picture is not taken and the lens housing is protractedfrom the camera housing when the picture is taken.

Although a variety of disclosures have been made relating to the barrieropening/closing mechanism for use in a collapsible type camera with thebarrier of the type described above, a structure revealing both anextremely simple structure and easy handling has not as yet beendisclosed.

For example, a barrier opening/closing mechanism has been disclosed inU.S. Pat. No. 4,864,338 which is arranged in such a manner that, whenthe lens housing is retracted, a portion of a barrier opening/closingmember, which is arranged to be moved in synchronization with themovement of the lens housing, is engaged with a cam surface of anengagement member provided in the camera housing so that the barrier isclosed. That is, the above-described barrier opening/closing mechanismis arranged in such a manner that a slide lever is provided for atransmission shaft which projects from the barrier opening/closingmember disposed adjacent to the lens housing toward the camera housing.The slide lever is arranged to be selectively engaged with the camsurface of the engagement member disposed in the camera housing. Theportion including the slide lever is forcibly rotated by the cam surfaceagainst the urging force of a spring which always urges the barrier inthe opening direction. As a result, the barrier is opened/closed via thebarrier opening/closing member including the transmission shaft.

The above-described conventional barrier opening/closing mechanism isarranged in such a manner that the slide lever which is urged by thesimple tension spring in a direction in which the barrier is opened andthe cam surface having a simple slope are engaged to each other so thatthe movement in the direction of the optical axis of the lens isconverted into a rotary motion. Therefore, the structure is not providedwith means for preventing a change in the urging force of the springacting on the slide lever. As a result, a problem arise in terms of apractical use. That is, the urging force of the spring is determined bythe length of its elongation in accordance with the degree of therotation of the slide lever, the spring acting on the slide lever whichis engaged to the cam surface so as to be rotated while moving insynchronization with the rectilinear motion of the lens housing in thedirection of the optical axis of the lens. As a result, the quantity offorce (driving force) necessary to rectilinearly move the lens housingat the time of opening/closing the barrier becomes inequal. Therefore, auser feels uneasy because the retraction/protraction action of the lenshousing cannot be smoothly performed. In particular, since collapsiblecameras of the type described above usually use an electric motor so asto retract/protract the lens housing, the above-described inequal forcecauses the load of the electric motor acting on the lens housing drivingsystem to be changed. Therefore, a problem arises in that vibrations andnoise generated in the motor and/or the gear configuration and thechange in the driving speed of the lens housing can be perceived by auser. What is even worse, if the battery has been consumed, the outputfrom the motor is lowered excessively, causing the lens housing to bestopped at an intermediate position. The change in the moving forceexerts a bad influence upon the mirror housing driving system and thecam engagement portion. In particular, a partial and eccentric wear willdeteriorate the durability, causing a critical problem to take placewhen used practically.

In particular, the above-described lens housing driving system and thebarrier opening/closing mechanism must be able to smoothly operate whilepreventing the change in the load to be applied to the lens housing. Inaddition, there has been a desire to improve the durability of each ofthe above-described system and the mechanism. Thus, there arises anecessity of providing a structure capable of overcoming theabove-described problems.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a lens driving devicecapable of smoothly rectilinearly moving a lens group and reducing thelength of a guide member, the lens driving device being for use in acamera the size and the thickness of which are reduced.

Another object of the present invention is to provide a reliable lightleakage prevention device capable of overcoming the above-describedproblems.

A further object of the present invention is to provide an electricsignal transmission device for a zoom lens or a multifocus lens camerain which an FPC for establishing a connection between an electric deviceprovided for the camera housing and an electric device provided for thelens portion can be smoothly accommodated in such a manner that theimage quality cannot be deteriorated by a ghost or obstruction.

A still further object of the present invention is to provide a barrieropening/closing mechanism for use in a collapsible camera with a barrierand capable of making the load to be substantially constant, the loadacting on a cam surface of a barrier opening/closing cam foropening/closing the barrier disposed on the front surface of an imaginglens in synchronization with the protraction/retraction action of a lenshousing.

In order to overcome the above-described problems, as shown in thedrawings, an aspect of the present invention lies in a lens drivingdevice comprising a holding member 5 for holding imaging lenses 14 andhaving a first helicoid 5a formed relative to the optical axis of thelenses 14a and 14b; a rotary member 6 having a second helicoid 6b whichis arranged to engage to the first helicoid 5a, the rotary member beingarranged to be engaged to the holding member 5 via the two helicoids 5aand 6b and rotatably supported relative to the optical axis to a camerahousing 17; a guide member 12 which is provided for either of theholding member 5 or the camera housing 17 and which extends in thedirection of the optical axis; and supporting members 25 and 26 providedfor the residual one of the holding member 5 and the camera housing 17to which the guide member is brought into contact, whereby the rotationof the holding member 5 is prevented by the contact between the guidemember 12 and the supporting members 25 and 26 and allows the holdingmember 5 to rectilinearly move in the direction of the optical axis inaccordance with the rotation of the rotary member 6. The guide member 12has two parallel surfaces which are perpendicular to the tangent of acircle centering the optical axis. The supporting members 25 and 26comprise a pair of annular bodies 25 each of which has a conical surfacewhich is rotatable relative to an axis perpendicular to the opticalaxis. The supporting members 25 and 26 come in contact with the twoparallel surfaces of the guide member 12 at the above-described conicalsurfaces.

According to the present invention, the rectilinear movement key of acamera can be shortened and the size and the thickness of the camera canthereby be reduced. Furthermore, since the rectilinear movement keyserving as a guide member for rectilinearly moving the lens housing isin the form of a plate and has a proper elasticity, the parallelism ofits two sides can be maintained even if it is deflected when the lenshousing is rectilinearly moved. Furthermore, the supporting member whichcomes in contact with the parallel two surfaces is in the form of atleast one pair of rollers having a rotatable conical surface. Therefore,a play or a catch can be prevented between the lens housing and therectilinear movement key.

In order to overcome the above-described problems, an aspect of thepresent invention lies in a light leakage prevention device for a camerahaving a lens housing 5 which is able to project and move from anopening formed in a camera housing 17 in the direction of the opticalaxis, the light shielding device having a light shielding member 29disposed in the opening of the camera housing 17 in such a manner thatit comes in contact with the outer surface of the lens housing 5.Furthermore, a cylindrical portion 29b is disposed in the periphery ofthe light shielding member 29.

Furthermore, a light leakage prevention device is constituted in whichone or more grooves 29d are formed in a portion in which the lightshielding member 29 slides and comes in contact with the lens housing 5.

In addition, a light leakage prevention device is constituted in whichthe light shielding member is in the form of a plate ring made of anelastic material, the light shielding member 29 being integrally formedwith a metal holding member 29e.

Since the light shielding member slides and comes in contact with theouter surface of the lens housing, light leakage taken place due to aneccentricity can be prevented. Therefore, the diagonal light can bestopped by the cylindrical portion disposed in the periphery portion.Since grooves are formed in the contact portion, the slide resistancecan be reduced at the time of the rectilinear movement of the lenshousing. In addition, sliding can be smoothly performed since thedeformation of the light shielding member can be reduced.

In order to overcome the above-described problems, an aspect of thepresent invention lies in an electric signal transmission device for acamera including a camera housing 17; a holding member 5 for holding alens and having a first helicoid 5a formed relative to the optical axisof the lens; a rotary member having a second helicoid 6b which isarranged to engage to the first helicoid 5a, the rotary member 6 beingarranged to be engaged to the holding member 5 via the two helicoids androtatably supported relative to the optical axis to the camera housing;a guide member 12 disposed on the inside of the rotary member 6 in sucha manner that its end portion is secured to the camera housing 17 andthe guide member extends from the position at which the end portion issecured to the camera housing in the direction of the optical axis, theguide member 12 converting the rotary motion of the rotary member 6 intoa rectilinear motion of the holding member 5 in the direction of theoptical axis; a first electric device supported by the camera housing17; a second electric device supported by the holding member 5; and aflexible substrate 27 establishing an electrical connection between thefirst and second electrical devices, the electric signal transmissiondevice comprising: a fastening portion 27d secured to the camera housing17, a deflection portion 27c connected to the fastening portion 27d, anextension portion 27b connected to the deflection portion 27c andextending on the inside of the rotary member and another fasteningportion 27a connected to the extension portion and secured to theholding member, wherein the extension portion 27b is disposed betweenthe rotary member 6 and the guide member 12 in such a manner that theextension portion 27b is positioned in contact with the guide member 12and is able to move on the guide member 12 when the holding member 5rectilinearly moves.

Another aspect of the present invention lies in an electric signaltransmission device wherein the deflection portion 27c is accommodatedin a space formed outside the rotary member 6.

Another aspect of the present invention lies in an electric signaltransmission device characterized in that the first electric deviceincludes collimator means 31 and 32 having a light emitting portion 31and a light receiving means and a photometry means disposed between thelight emitting portion 31 and the light receiving portion 32, the spacebeing a space formed between the light emitting portion 31 and the lightreceiving portion 32 and behind the photometry means.

According to the present invention, the flexible substrate is disposedbetween the rotary member and the guide member in such a manner that itis able to slide and its surface facing the optical axis is shielded bythe guide member. Therefore, the image cannot be damaged due to thereflection of the diffused light.

Since the flexible substrate is deflected in a sufficiently large spacedisposed outside the rotary member, it does not obstruct the opticalpath and is not damaged due to excessive bending, causing the durabilityto be improved.

In order to overcome the above-described problems, an aspect of thepresent invention lies in an electric signal transmission device for acamera including a camera housing 17; a holding member 5 for holding alens and having a first helicoid 5a formed so as to have an axial centercorresponding to the optical axis of the lens; a rotary member 6 havinga second helicoid 6b engaged with the first helicoid 5a in a screwingmanner, the rotary member 6 being arranged to engage with the holdingmember through the two helicoids while being supported on the camerahousing so as to be rotatable on the optical axis; a guide member 12disposed on the inner circumferential side of the rotary member 6 insuch a manner that its end portion is secured to the camera housing andthat it extends from this secured portion in the direction of theoptical axis, the guide member 12 converting the rotary motion of therotary member 6 into a rectilinear motion of the holding member 5 in thedirection of the optical axis; a first electric device supported on thecamera housing 17; a second electric device supported by the holdingmember 5; and a flexible substrate 27 establishing an electricalconnection between the first and second electrical devices. In thiselectric signal transmission device, the flexible substrate 27 includesa fastening portion 27d secured to the camera housing 17, a deflectionportion 27c connected to the fastening portion 27d, an extension portion27b connected to the deflection portion 27c and extending on the innercircumferential side of the rotary member and another fastening portion27a connected to the extension portion and secured to the holdingmember. The extension portion 27b is disposed between the rotary member6 and the guide member 12 in such a manner as to be in contact with theguide member 12 and to be able to slide on the guide member 12 when theholding member 5 moves rectilinearly. The deflection portion isaccommodated in an accommodation chamber 31 provided on the outercircumferential side of the rotary member 6. There is also provided alimit member 17b for enabling formation of a deflected shape of thedeflection portion 27c and for constantly limiting the direction ofdeflection thereof. The limit member 17b is formed integrally with amember forming the accommodation chamber 31.

According to the present invention, the flexible substrate is deflectedin the sufficiently large accommodation chamber outside of the rotarymember, the limit member constantly enables the deflection portionconnected to the fastening portion defining one end of the flexiblesubstrate to be formed into a deflected shape, and applies a force tothe deflection portion such that the deflection portion can be turnedsmoothly and the direction of deflection is constantly limited.

The flexible substrate is comparatively reduced in length.

The limit member for enabling formation of the deflected shape is formedintegrally with a member which forms the accommodation chamber.

Furthermore, an aspect of the present invention lies in a barrieropening/closing mechanism comprising a barrier opening/closing camdisposed in the camera housing. The barrier opening/closing cam has acam lever disposed for opening/closing a lens protection barrierdisposed on the front surface of an image lens, the cam lever beingalways rotatably urged by a spring in the direction in which the barrieris opened. The barrier opening/closing cam is further provided with acam surface which is engaged to the cam lever by the movement of the camlever in the direction of the optical axis of the lens so that thebarrier is opened/closed. The cam surface of the barrier opening/closingcam is arranged to be formed in accordance with the magnitude of theurging force of the spring in such a manner that the angle ofinclination is large in a range in which the urging force of the springacting on the cam lever is large and the angle of inclination is smallin a range in which the urging force is small.

According to the present invention, the angle of inclination is large inthe portion in which the barrier opening/closing cam is engaged to thecam surface is large in a range in which the urging force of the springacting on the cam lever is large. Therefore, the load at the time of therectilinear movement of the lens housing can be reduced. In a range inwhich the urging force of the spring is small, the angle of inclinationin the fastening portion is small. Therefore, the load to the lenshousing can be made substantially the same as the above-described case.Therefore, a substantially constant load is able to act the drivingsystem for rectilinearly moving the lens system regardless of themagnitude of the urging force of the spring acting on the cam lever.

Other and further objects, features and advantages of the invention willbe appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view which illustrates a conventional lensdriving mechanism;

FIGS. 2A and 2B are plan views which respectively illustrate aconventional rectilinear movement key;

FIG. 3 is a perspective view which illustrates an embodiment of a frontbody and a lens driving mechanism according to the present invention;

FIG. 4 is a vertical cross sectional view which illustrates a portionincluding the optical axis of a lens;

FIG. 5 is a cross sectional view taken along line V--V of FIG. 4;

FIG. 6A is a cross sectional view which illustrates a lens drivingmechanism at the telescoping position;

FIG. 6B is a longitudinal cross-sectional view including the opticalaxis of the lens in a state where the power source is turned off;

FIG. 7 is a cross sectional view which illustrates a light shieldingmember;

FIG. 8 is a schematic cross sectional view which illustrates anotherembodiment;

FIG. 9 is a plan view which illustrates a camera;

FIG. 10 is a schematic exploded perspective view which illustrates alens housing portion of a collapsible camera with a barrier according toan embodiment of a barrier opening/closing mechanism according to thepresent invention;

FIGS. 11 and 12 are schematic structural views which respectivelyillustrate the opening/closing action of the barrier when viewed fromthe front portion of the lens housing;

FIG. 13 illustrates the relationship between the cam lever and the camsurface which is the characteristics of the present invention;

FIGS. 14A, 14B and 14C are schematic views which illustrate theprotraction/retraction operation of the lens housing of the collapsiblecamera;

FIGS. 15A and 15B illustrate the relationship of the force when thefastening position is changed; and

FIGS. 16, 17A and 17B are schematic view which illustrate a problemexperienced with the conventional structure having a cam surface havinga simple slanted surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3 is an exploded perspective view which illustrates a front housingand a lens driving mechanism according to an embodiment of the presentinvention. FIG. 4 is a vertical cross sectional view which illustrates aportion including the optical axis of a lens of a camera according tothe same, wherein a wide angle position at which the lens has beenretracted is illustrated. FIG. 5 is a cross sectional view taken alongline V--V of FIG. 4 and illustrates the lens driving mechanism whenviewed from a rear portion of the optical axis after the lens drivingmechanism has been cut by a rear lens chamber including the rear guidepin. FIG. 6A is a vertical cross section which illustrates a cameraincluding the optical axis of the lens, in which a telescopic positionat which the lens has been protracted is illustrated.

A lens housing 5 is accommodated in an inner helicoid (rotary member) 6.A helicoid 5a formed on the outer surface of the lens housing 5 isengaged to another helicoid 6b formed on the inner surface of the innerhelicoid 6. A front lens chamber 7 is accommodated in the forward innerportion of the lens housing 5 and a shutter (omitted from illustration)is disposed on the outside of the front portion of the lens housing 5.

A rear cam ring 8 is disposed inside the lens housing 5 and as well ason the outside of the rear rectilinear movement guide cylinder (guidemember) 9 in such a manner that it can rotate. The rear cam ring 8 has,in the annular portion thereof, three cam grooves 8b each of which isdiagonally formed in the circumferential direction. The rear cam ring 8has two elongated holes 8a at the rear flat portion thereof. Theelongated holes 8a form guide portions into which two round projectionportions 10a formed on a clutch 10 can be movably introduced when theclutch 10 is brought into contact with the above-described rear flatportion of the rear cam ring 8.

The clutch 10 is fastened to the rear cam ring 8 by a fixing screw 11whereby the position at which the clutch 10 is secured can be shifted byloosening the fixing screw 11 in a range of the elongated hole 8a formedin the rear cam ring 8. The clutch 10 is slidably fitted with the innerhelicoid cylinder 6 at a linear groove 6c formed in the inner helicoidcylinder 6.

Three linear grooves 9a are formed in the rear rectilinear movementguide cylinder 9 at positions at which the circumference is divided intothree sections. A flat slidable surface (omitted from illustration)which is arranged to slide on a rectilinear movement key (guide member)12 is, in parallel to the optical axis, formed in the central portion ofthe outer surface of the rear linear guide cylinder 9. Furthermore,elongated portions (omitted from illustration) running parallel to theoptical axis are respectively formed on the two sides of the slidablesurface in the circumferential direction. The rear rectilinear movementguide cylinder 9 is fixed and thereby integrated with the lens housing 5by rectilinear movement guide fixing screws 13.

A rear lens chamber 14 accommodates lenses 14a and 14b in a fixedmanner. Three rear guide pins 15 are driven into the outer surface ofthe rear lens chamber 14 in the radial direction at positions whichdivide the circumference into three sections. The three rear guide pins15 are respectively fitted within the cam grooves 8b formed in the rearcam ring 8 and the rectilinear movement grooves 9a formed in the rearrectilinear movement guide cylinder 9 so that a cam follower isestablished.

A rear play-prevention spring 16 presses each of the rear guide pins 15to the rear wall of the cam grooves 8b so that the play of the rear lenschamber 14 in the direction of the optical axis is prevented.

The inner helicoid 6 is in the form of a cylinder and is accommodated ina cylindrical space formed in a front body 17 in such a manner that itis rotatably held in the front body 17 at an annular projection 6dformed on the outer surface of the inner helicoid 6 by a retaining plate18 fixed by screws 19 which are inserted into screw holes 18a.

A flexible printed circuit (to be abbreviated to an "FPC" hereinafter)encoder FPC 20 is adhered to the outer surface of the inner helicoid 6in such a manner that its encoder pattern (omitted from illustration)which is an electric contact faces outwards. An encoder brush 21 isfixed to the front body 17 by an encoder brush fixing screw 22 in such amanner that a contact 21a at each of the front portions of the encoderbrush 21, through a cut portion in the lower portion of the front body17, comes in contact with the encoder FPC 20 applied to the innerhelicoid 6.

The rectilinear movement key 12 is in an elongated flat plate-like shapehaving parallel planes on the two sides thereof, the rectilinearmovement key 12 being secured to a rear body 23 in an upper portion atan end portion thereof by rectilinear movement key fixing screws 24. Therectilinear movement key 12 serves as a guide member extending forwardsbetween the rear cam ring 8 and the rear rectilinear movement guidecylinder 9 from the rear body 23 in parallel to the optical axis. Therectilinear movement key 12 is positioned on a smooth and flat portionon the top surface of the rear rectilinear movement guide cylinder 9 andis movably held between a pair of rollers provided for the rearrectilinear movement guide cylinder 9 in the direction of the opticalaxis.

Each roller 25 has a conical surface on the side thereof. A pair of therollers 25 are respectively fastened by roller screws 26 inserted intoroller screw holes 9b formed in two elongated portions of the rearrectilinear movement guide cylinder 9 in such a manner that each rollercan freely rotate about the axis of the conical surface.

The pair of the rollers 25 are arranged in such a manner that they comein linear contact with the parallel planes on the two sides of therectilinear movement key 12.

In the thus constituted structure, since the rectilinear movement key 12elongates in the direction of the optical axis and has a reducedthickness, it vertically deflects when viewed in FIG. 5 by a loadgenerated from the rollers 25 when the lens rectilinearly moves.Furthermore, each surface on which the rectilinear movement key 12slides on a roller 25 is arranged to be parallel to the direction inwhich the rectilinear movement key 12 deflects. The reason for this liesin that generation of a play or a catch between the rectilinear movementkey 12 and the rollers 25 must be prevented even if the rectilinearmovement key 12 is vertically deflected. As a result, the positionaldeviation between the rectilinear movement key 12 and the rollers 25generated due to the manufacturing error can be absorbed.

The shutter FPC 27 extends from a shutter driving member 28 positionedin the front portion on the outer surface of the lens housing 5, theshutter FPC 27 being positioned along the top surface of the rectilinearmovement key 12 which extends forwards from the rear body 23, that is,the shutter FPC 27 being positioned toward the rear body 23. It isfitted within a rectangular groove 12a formed in the top portion of therectilinear movement key 12. Furthermore, it is accommodated in anoverlapped manner in a space formed between the front body 17 and therear body 23.

A light shielding member 29 is positioned in contact with the outersurface of the front portion of the lens housing 5. FIG. 7 is a crosssectional view of the light shielding member 29 and a portion includingit. FIG. 8 is a cross sectional view which illustrates another exampleof the light shielding member 29.

The light shielding member 29 is a thin annular member having a largeround hole formed in the central portion thereof, the light shieldingmember 29 comprising an annular disc portion 29a and a generallycylindrical flange portion 29b formed at the periphery of the discportion 29a. The large round hole portion in the central portion of thedisc portion 29a has a band portion 29c and a groove portion 29d formedin the direction toward the lens housing 5. The light shielding member29 is arranged in such a manner that its holding member 29e ispositioned more adjacent to the optical axis than the periphery of thedisc portion 29a and farther from the optical axis than the band portion29c and the groove portion 29d, the holding member 29e being integrallyformed with the disc portion 29a.

The light shielding member 29 is disposed in such a manner that it canslide around the outer surface 5c of the front portion of the lenshousing 5 at a top 29f of the band portion 29c. Furthermore, the lightshielding member 29 is positioned in contact with a front surface 6e ofthe inner helicoid 6 at a surface 29g of the disc portion 29a adjacentto the inner helicoid 6 in such a manner that it can separate from thesame. The light shielding member 29 is, at a side surface 29h of thedisc portion 29a adjacent to the side portion 30a of the front cover 30adjacent to the subject, positioned in contact with an inner surface 30cof the side portion 30a of the front cover 30 adjacent to the subject insuch a manner that it can separate from the same.

The light shielding member 29 is made of silicone rubber and is fittedaround the lens housing 5 at its front outer surface 5c due to theelasticity thereof. Therefore, the diameter of the round hole formed atits central portion is smaller than the outer diameter of the lenshousing 5 by about 0.2 mm when measured in such a manner that the lightshielding member 29 does not come in contact with the front outersurface 5c.

The thickness of the disc portion 29a of the light shielding member 29in the direction of the optical axis is about 0.8 mm, the thickness ofthe band portion 29c in the same direction is about 0.2 mm and thedegree of the eccentricity is about 0.2 to 0.3 mm.

The reason why the light shielding member is made of silicone rubber andis positioned about the front outer surface 5c of the lens housing 5 insuch a manner that it is positioned in contact with the same lies inthat the pressure of the light shielding member 29 against the frontouter surface 5c must be made constant so as to prevent the lightleakage due to the change in the pressure. That is, in the case wherethe light shielding member 29 is provided for the inner helicoid 6, theinner helicoid is necessarily rotated. Therefore, if there is aneccentricity between the lens housing 5 and the inner helicoid 6, thepressure of the light shielding member 29 against the lens barrel 5 isinevitably changed. As a result, a gap is undesirably formed between theabove-described two members. Therefore, the light leakage cannot beperfectly prevented.

The shutter FPC 27 is, at its end portion 27a, fixed by a projection 28bformed on the shutter driving member positioned on the front outersurface of the lens housing 5. Its elongated portion 27b is elongatedfrom the shutter driving member 28 and is positioned between therectilinear movement key 12 and the inner helicoid 6, the rectilinearmovement key 12 being arranged in such a manner that an end portion issecured to the rear body 23 and extends. The shutter FPC 27 extendsforwards along the top surface of the rectilinear movement key 12 in therearward direction, that is, toward the rear body 23. At the end portionof the rectilinear movement key 12, it is fitted within a gap formed inthe rectangular groove 12a at the upwardly slanted portion which iscontinued to the end portion of the rectilinear movement key 12.Furthermore, its deflection portion 27c is, without being bent andthereby in a smooth shape, accommodated in a space formed between thefront body 17 and the rear body 23. The space formed between the frontbody 17 and the rear body 23 serves, as is shown from FIG. 9 which is aplan view of the camera, as a marginal space at the time of mounting theelectric elements, the space being disposed between a light emittingportion 31a and a light receiving portion 32 which constitute thecollimator means and behind a photometry means 33. The shutter FPC 27 issecured at a projection portion 17a formed on the front body 17, whileanother end portion 27d is introduced and connected to a control portion(omitted from illustration).

The space (accommodation chamber) formed between the front body 17 andthe rear body 23 is formed by an accommodation chamber member 17d whichis a part of the front body 17, and is closed at the rear side by anaccommodation chamber rear wall member 23a which is a part of the rearbody 23. These members are integrally formed with high accuracy suchthat their portions contacting the two side surfaces of the shutter FPC27 are smoothly formed without any joint. Inner side walls (not shown)of the accommodation chamber 31 are spaced by a distance close to thewidth of the shutter FPC 27 such that the shutter FPC can move smoothlyon them. The shutter FPC 27 is thereby prevented from moving laterallyand can be smoothly inserted in or drawn out of the the accommodationchamber 31.

An FPC limit member 17b is fixedly provided integrally with upper sidewall portions of the accommodation chamber member 17d so as to extendinwardly therefrom like a beam perpendicular to the optical axis andparallel to the surface of the rectilinear key 12.

An eave 17e is fixedly provided integrally with an upper fore wallportion of the accommodation chamber member 17d so as to extendrearwardly and to face the FPC restraining member 17b.

The FPC limit member 17b has a slant surface portion 17c facing the eave17e. The slant surface portion 17c has a smooth recessed surfaceextending straight in the longitudinal direction. If this smoothrecessed surface is approximated to a circularly cylindrical surface,the radius of curvature of this cylindrical surface is about 2 mm orlonger. If it is smaller than 2 mm, the shutter FPC 27 cannot besmoothly curved along the slant surface and is sharply bent so as to becreased always at the same position.

The shutter FPC 27 is fixed at a projection 17a and its portion locatedat the rear of this projection is led between the eave 17e and the FPCrestraining member 17b and is smoothly bent downwardly and forwardlyalong the slant surface portion 17c.

Referring to FIG. 4 which is a cross sectional view of the lens at thewide angle imaging operation in which the lens housing is retractedmaximum, the shutter FPC 27 is fully expanded in the cross sectionalspace formed between the front body 17 and the rear body 23. However,referring to FIG. 6A which is a cross sectional view of the lens at thetelescopic imaging operation in which the lens housing is protractedmaximum, the shutter FPC 27 is not expanded fully in the cross sectionof the space formed between the front body 17 and the rear body 23 sincethe looseness is reduced by a degree which corresponds to the forwardmovement of the shutter FPC 27, causing a marginal space to be formed.

Now, the operation of this embodiment will be described.

A motor (omitted from illustration) provided in the camera housing isoperated in response to a signal issued from a focal point detectiondevice (omitted from illustration), which is individually provided, thesignal denoting a command of forwards/rearwards moving the lens group. Adrive gear (omitted form illustration) connected to the above-describedmotor is rotated in response to the above-described command. Since amajor gear 6a formed on the outer surface of the inner helicoid 6 isengaged to the above-described drive gear, the inner helicoid 6 and theencoder FPC 20 applied to the outer surface of the inner helicoid 6 areintegrally rotated when the motor is rotated. At this time, the encoderpattern (omitted from illustration) formed on the surface of the encoderFPC 20 is electrically connected due to the slide contact of the encoderbrush front portion 21a provided for the encoder brush 21. As a result,the rotational angle of the inner helicoid 6 can be detected inaccordance with the fact whether or not the circuit is opened. After theinner helicoid 6 has rotated by an angular degree which corresponds tothe above-described command, a stop signal is transmitted so that therotation of the motor is stopped and the rotations of the other elementsconnected to the motor are stopped.

When the inner helicoid 6 commences to be rotated, the lens housing 5commences to be rotated via the helicoid 6b and the helicoid 5a which isengaged to the helicoid 6b. However, the rotation of the lens housing 5is restricted by the rectilinear movement key 12 as described above andit therefore performs only a rectilinear movement motion along theoptical axis.

When the inner helicoid 6 is rotated, the rear cam ring 8 is engaged tothe rectilinear movement groove 6c so that the rear cam ring 8 isrotated together with the inner helicoid 6 via the clutch 10, which isengaged to the rear cam ring 8.

The rotation of the rear rectilinear movement guide cylinder 9 isrestricted by the rectilinear movement key 12 which is held by the pairof rollers 25 which are fixed by the screws. As a result, the rearrectilinear movement guide cylinder 9 performs only the rectilinearmovement. Since the side surface of the rollers 25 are in the form of acone, the rollers 25 freely rotate at the time of the forward/rearwardmovement of the rectilinear movement guide cylinder 9. The side surfacesof the rectilinear movement key 12 are held by the rollers 25 which arepositioned on the two sides thereof and which rotate so as to formparallel planes. Therefore, the rectilinear movement key 12 comes incontact the rear rectilinear movement guide cylinder 9 so that it isrectilinearly guided via the rollers 25. Since the rectilinear movementkey 12 has proper elasticity, the two side surfaces maintain theparallelism even if they are deflected in parallel to each other. As aresult, the linear contact with the rollers 25 can be maintainedsatisfactorily. Furthermore, since the rear rectilinear movement guidecylinder 9 is secured to lens housing 5 by the rear rectilinear movementguide cylinder fixing screws 13, they are able to integrallyrectilinearly move.

When the rear cam ring 8 is rotated, its rotation is transmitted to therear lens chamber 14 via the rear guide pins 15 which are inserted intothe cam grooves 8b. However, its rotation is limited by the rectilinearmovement grooves 9a formed in the rear rectilinear movement guidecylinder 9 into which the rear guide pins 15 are inserted. Therefore,the rear lens chamber 14 is only rectilinearly moved. The reason forthis lies in that the rotation of the rear rectilinear movement guidecylinder 9 is restricted by the rectilinear movement key 12. The rearlens chamber 14 performs a relative rectilinear movement with respect tothe rear rectilinear movement guide cylinder 9 in accordance with themovement of the cam grooves 8b. Therefore, the positional relationshipbetween the front lens group which is integrally rectilinearly movedtogether with the lens housing 5 and the rear lens group is changed to apredetermined interval. As a result of this, zooming is performed. Atthis time, since the rear lens chamber 14 is always pressed against therear wall of the cam grooves 8b by the rear play prevention spring 16,the fitting of the cam grooves 8b to the rear guide pins 15 may beperformed while maintaining a sufficient margin. The shutter FPC 27extends from the shutter driving member 28 disposed in the lens housing5 and slides upwards on the top surface of the rectilinear movement key12 along the rear body 23. Furthermore, it has a loose portion in thespace formed between the front body 17 and the rear body 23. Therefore,the length of the shutter FPC 27 can be automatically adjusted inaccordance with the forward/rearward movement of the lens housing 5 insuch a manner that the length of protraction is enlarged and the looseportion is shortened when the lens housing 5 has been protracted.Furthermore, when the lens housing 5 is retracted, the length of theprotraction is shortened and the loose portion is elongated.

The lens housing 5 is deeply retracted into the camera housing throughthe opening portion formed in the camera housing at the time of the wideangle imaging operation. Since the light shielding member 29 surroundsand comes in contact with the lens housing 5 at this time, it isretracted together with the lens housing 5 due to the slide resistance.The distance of the retraction is restricted by the inner helicoid 6 tobe shorter than the lens housing 5. As a result, it comes in contactwith the front surface 6e of the inner helicoid 6 on the surface 29a ofthe disc portion 29a adjacent to the inner helicoid 6.

At the time of the telescopic imaging operation, the lens housing 5protracts from the camera housing through the opening portion formed inthe camera housing. At this time, since the light shielding member 29comes in contact around the outer surface of the lens housing 5, itmoves forwards together with the lens housing 5 due to the slideresistance. The distance of the forward movement is restricted by thefront cover 30 to be smaller than the lens housing 5. As a result, thelight shielding member 29 comes in contact with the inner surface 30c ofthe side portion 30a of the front cover 30 adjacent to the subject atits side surface 29h adjacent to the portion 30a of the front cover 30adjacent to the subject.

At the time of the telescopic imaging operation, the lens housing 5moves forwards before the light shielding member 29 comes in contactwith the front cover 30. As a result, a gap is formed between the lightshielding member 29 and the lens housing 5. Since the cam 8 has threediagonal cam grooves 8b in the circumferential direction and the rearrectilinear movement guide cylinder 9 has three rectilinear movementgrooves 9a at positions at which the circumference is divided into threesections, light from the above-described gap is able to leak through theabove-described grooves.

FIG. 8 is a schematic cross sectional view of an example arranged insuch a manner that a light shielding member 34 is not provided with acylindrical portion. Therefore, light diagonally or perpendicularly madeincident or dispersed cannot be stopped. As a result, light leakagecannot be prevented.

FIG. 7 is a cross sectional view of the light shielding member accordingto this embodiment of the present invention.

As shown in FIG. 7, in the light shielding member 29 having thecylindrical portion 29c according to the present invention, the edge 29bof the cylindrical portion 29c is introduced into the gap between theinner helicoid 6 and the front cover 30. Therefore, the diagonal orvertical incident or scattering light with respect to the optical axisis stopped.

Therefore, the cylindrical portion 29c must have a size which issufficient to shield the gap between the inner helicoid 6 and the frontcover 30.

In the above-described structure, the light shielding member 29 isslidable and comes in contact with the lens housing 5 at a round holehaving a relatively smaller diameter. Therefore, it clamps the lenshousing 5 with a small constant force without an influence of theeccentricity taken place at the time of the manufacturing or theassembling work.

The light shielding member 29 is integrally formed by using rubber of agood quality and a rigid body and the two band portions are formed onthe lens housing 5 with respect to the groove. Therefore, it can beelastically deformed by a constant pressure and slide by a small load.

The extension portion 27b of the shutter FPC 27 extends along the topsurface of the rectilinear movement key 12 toward the rear body 23 fromthe projection portion 28b formed in the shutter driving member 28 towhich an end portion of the shutter FPC 27 is secured. At the endportion of the rectilinear movement key 12, it is disposed upwards inthe gap formed in the rectangular groove 12a. Then, it is accommodatedin a smooth shape in the space formed between the front body 17 and therear body 23 in such a manner that the deflection portion 27c is notbent. The shutter FPC 27 slides in the rectilinear movement key 12 andthe rectangular groove 12a when the lens housing 5 movesforwards/rearwards.

At the time of the wide angle imaging operation in which the lenshousing 5 is retracted maximum, the shutter FPC 27 is fully expanded inthe cross section of space formed between the front body 17 and the rearbody 23. However, at the time of the telescopic imaging operation inwhich the lens housing 5 is protracted maximum, the shutter FPC 27 isprotracted so that the looseness in the space formed between the frontbody 17 and the rear body 23 is reduced.

As shown in FIG. 4 with respect to a cross section of the lens, when thelens barrel is positioned for wide angle shooting, the shutter FPC 27 isaccommodated in the interior space of the accommodation chamber 31formed between the front body 17 and the rear body 23 in such a manneras to meander largely as viewed in the cross section.

At this time, as in the case of telephoto shooting, the shutter FPC 27is fixed at the projection 17a, its portion located at the rear of thisprojection is led between the eave 17e and the FPC limit member 17b andis forced forwardly by the slant surface portion 17c of the FPC limitmember 17b, and a force is applied constantly and forwardly to theshutter FPC 27. The shutter FPC 27 is smoothly bent forwardly anddownwardly by the slant surface portion 17c, extends forward to a fullextent such as to contact the fore wall of the accommodation chamber 31and then the lower wall, and is then led rearwardly. Since in this casethe deflection portion 27c is long, this portion extends rearwardly andfully in the accommodation chamber 31 to reach an upper rear portion ofthe same and to contact the rear body 23, and is led to the gap of arectangular groove 12a.

When the lens barrel is positioned for telephoto shooting, the shutterFPC 27 is fixed at the projection 17a, its portion located at the rearof this projection is led between the eave 17e and the FPC limit member17b to be turned downward and is forced forwardly while being furtherturned by the slant surface portion 17c of the FPC limit member 17b, anda force is applied constantly and forwardly to the shutter FPC 27. Theshutter FPC 27 is bent forcibly and smoothly to be turned forwardly anddownwardly along a smoothly curved surface of 2 mm or more in terms ofradius of curvature of the slant surface portion 17c, but it is ledrearwardly without contacting the fore wall of the accommodation chamber31. Since in this case the deflection portion 27c is short, this portiondoes not extend fully in the accommodation chamber 31 while extendingrearwardly and does not contact the upper rear potion of the rear body23, and is led to the gap of the rectangular groove 12a.

As shown in FIG. 6B with respect to a longitudinal cross section of thelens containing the optical axis, when the power source is turned off,that is, when the lens barrel is retracted to the innermost position,the shutter FPC 27 extends fully in the interior space of theaccommodation chamber 31 formed between the front body 17 and the rearbody 23 while meandering and folding up several times as viewed in thecross section.

At this time, as in the case of telephoto shooting, the shutter FPC 27is fixed at the projection 17a, its portion located at the rear of thisprojection is led between the eave 17e and the FPC limit member 17b andis forced forwardly by the slant surface portion 17c of the FPC limitmember 17b, and a force is applied constantly and forwardly to theshutter FPC 27. The shutter FPC 27 is smoothly bent forwardly anddownwardly by the slant surface portion 17c, extends forward to a fullextent such as to contact the fore wall of the accommodation chamber 31and then the lower wall, and is then led rearwardly. Since in this casethe deflection portion 27c is long, this portion is further bent twotimes to form a loop without extending straight to the rear, thenextends fully to the upper rear portion of the accommodation chamber 31,contacts the rear body 23, and is led to the gap of a rectangular groove12a.

Thus, the formation of a suitable deflected shape enabled by the slantedsurface portion 17c of the FPC limit member 17b ensures that even whenthe power source is turned off and when the greater part of the shutterFPC 27 is retracted in the accommodation chamber 31, the shutter FPC 27is not sharply bent or twisted and is not reversely turned to the rear.A sufficient space for accommodation of the shutter FPC 27 is thusprovided and the shutter FPC 27 can be accommodated regularly.

In the case where the number of the lens group exceeds 3, the sameeffect can, of course, be obtained from a similar structure. In amultifocus lens having no zooming function, the shutter FPC 27 isarranged to be a similar structure and smoothly slides on therectilinear movement key 12 before it is accommodated in the upperspace.

According to this embodiment, the structure is arranged in such a mannerthat the supporting member which comes in contact with the two parallelsurfaces of the rectilinear movement key for rectilinearly moving thelens housing is arranged to be a pair of rotatable rollers each of whichhas a conical surface. Therefore, there is provided a lens drivingdevice which can be suitably provided for a camera the size and thethickness of which are desired to be reduced.

Furthermore, since the lens groups are able to smoothly rectilinearlymove at the time of changing the focal distance, the deterioration inthe image quality due to the defective slide can be prevented and thepower consumption can be reduced.

In addition, since the front lens housing and the rectilinear movementkey are not coupled to each other by using a hole, an eccentricfuzziness due to a catch can be prevented.

Furthermore, the accuracy necessary to manufacture the rectilinearmovement key and the rollers and the like can be made suitable.

In a multifocus lens having no zooming function, the movements of therectilinear moving lens groups can be smoothly completed with a similarstructure.

The degree of the parallelism of the two side surfaces of therectilinear movement key 12 is sufficient if the rotation of the rearrectilinear movement guide cylinder 9 can be restricted and the slidingoperation can be performed without occurrence of a looseness and thecatch at the time of the rectilinear operation. Therefore, the necessaryaccuracy level can be lowered. In addition, each of the planes can bedissociated from a plane.

According to this embodiment, the light shielding member made ofsilicone rubber is positioned in contact with the outer surface of thelens housing and the light leakage due to the eccentricity taken placeat the time of the manufacturing or assembling work can be prevented.

Furthermore, since the cylindrical portion is provided in its periphery,the diagonal or vertical light incidence can be prevented.

In addition, since the light shielding member is integrally formed witha rigid body by using silicone rubber and it slides on the surfacehaving the groove portion and the band portion, the slide resistance canbe reduced at the time of the rectilinear movement of the lens housingand the load at the time of driving the lens housing can be alsoreduced.

Furthermore, the manufacturing accuracy for the elements can be madesuitable and the assembling of these elements can be easily completed,causing the manufacturing cost to be reduced.

According to this embodiment, the light diffusion to the film surfacedue to the light reflection on the FPC can be prevented and theobstruction of the optical path can be perfectly prevented.

Since the FPC can be accommodated in a sufficiently large space and isnot bent excessively, the durability can be improved.

Furthermore, the marginal space which is provided for mounting theelectric elements and which is positioned between the light emittingportion and the light receiving portion of the collimator means andbehind the photometry means can be efficiently utilized.

Since the necessity of the coating work or the like necessary to preventthe reflection on the FPC can be eliminated, the manufacturing cost canbe reduced.

Furthermore, in the conventional structure, a member for guiding the FPCmust be provided separately from the rectilinear movement key. However,since in the invention the guide member can be arranged to act as therectilinear movement key, the manufacturing cost can be reduced.

According to the present invention, the flexible substrate can be bentin the accommodation chamber outside the rotary member, which chamberhas a sufficiently large interior space, and the limit member for alwaysenabling formation of a deflected shape of the flexible substrate limitsthe direction of deflection of the deflection portion of the shutter FPCconnected to the fixed end portion of the same. The deflected portioncan therefore be accommodated always regularly at the time of telephotoor wide angle shooting or even in the power-off state.

The shutter FPC is free from damage due to forcible bending or the likeand is therefore improved in durability.

The length of the shutter FPC is limited, which effect enables areduction in cost.

Since the limit member for formation of a deflected shape is formedintegrally with the member forming the accommodation chamber, it isimproved in accuracy and enables the shutter FPC to be bent smoothlywhile avoiding any increase in cost.

FIGS. 10 to 13 respectively illustrate an embodiment of a collapsiblecamera with a barrier to which a barrier opening/closing mechanismaccording to the present invention is applied. First, the schematicstructure of the lens housing portion of the camera will be brieflydescribed with reference to FIG. 10. Reference numeral 5 represents alens housing in which imaging lens groups (omitted from illustration)are included. The lens housing 5 has an inwardly-directed flange 5bformed at its front end portion thereof, the flange 5b having a barrieroperation ring 35 and two barriers 36 which can be opened/closed due tothe rotation motion of the barrier operation ring 35 in such a mannerthat the two barriers 36 cover the above-described imaging lens group.The two barriers 36 are disposed in such a manner that they can rotateand swing. Furthermore, the front-end portion of each of the barriers 36is covered by a front ring 37 which is fixed to the lens housing 5 by ascrew so that the two barriers 36 are integrally and rotatably fastenedin a space in the front end portion of the lens housing 5.

The barrier driving ring 35 comprises a cam lever 38 projecting from aportion thereof into the lens housing 5 along the direction of theoptical axis of the lens and a spring retainer 35a which projects on theperiphery of the same. The barrier driving ring 35 is rotatably disposedin the front cylindrical portion 5c of the lens housing 5. The cam lever38 is inserted into the lens housing 5 via a circular arc groove 5dformed in the inwards-directed flange 5b in such a manner that the camlever 38 can be rotated by a predetermined angular degree. A cam surface39a to be described later is formed at the front end portion of abarrier opening/closing cam 39 which projects along the inner surface ofthe lens housing 5 in the direction of the optical axis of the lens, thebase portion of the barrier opening/closing cam 39 being fixed, byscrews, from the back side of a black box 17 which constitutes a portionof the camera housing. The cam surface 39a is arranged so as to confrontthe cam lever 38. The above-described cam lever 38 and the cam surface39a are arranged to selectively engage to each other at the time of theprotraction/retraction of the lens housing 5.

A spring 40 is fitted to the spring retainer 35a of the barrieroperating ring 45, the spring 40 always urging the barrier operatingring 45 in the direction (designated by an arrow a) in which thebarriers 36 are opened. The other end portion of the spring 40 is fittedto a spring retainer 5e which projects on the inwards-directed flange 5of the lens housing 5. Reference numeral 5f represents a stop whichprojects to the inner periphery of the inwards-directed flange 5b andwhich holds the barrier operating ring 35 while having the barrieroperating ring 35 rotatably supported by a guide cylinder portion 59.

Two fastening claws 35b, which are fastened to fastening pins 36bprojecting adjacent to rotational shafts 36a which correspond to theinwards-directed flanges 5b of the barriers 36, are disposed at twoopposing positions on the outer periphery of the barrier operating ring35. As a result, the urging force of the spring 40 at the time of theengagement is made to act on the barriers 36. Reference numeral 5hrepresent bearings of the rotational shafts 36a provided for theinwards-direction flange 5b so that each of the barriers 36 is supportedrotatably relative to the above-described bearings 5h. Reference numeral41 represents coil springs wound around the front portions of theabove-described rotational shafts 36a. The coil springs 41 are disposedbetween the above-described fastening pins 36b and the front cylinderportion 5c of the lens housing 5. As a result, the barriers 36 are urgedin the directions designated by arrows b, that is, in the closingdirection (see FIGS. 11 and 12).

The helicoid 5a, which is engaged to the helicoid 6b formed on the innersurface of the intermediate helicoid 6 which is rotatably supportedadjacent to the black box 17, is formed on the outer surface at the rearend of the lens housing 5. Furthermore, the rotational force from anelectric motor 42 transmitted via a gear configuration (omitted fromillustration) is arranged to be transmitted to the gear portion 6aformed on the outer surface of the intermediate helicoid 6. As a result,the above-described lens housing 5 is protracted/retracted by theengagement of the helicoids 5a and 6b. The lens housing 5 is constitutedin such a manner that it does not rotate but only rectilinearly moves bythe rectilinear movement guide portion 39b of the barrieropening/closing cam 39. In FIG. 10, reference numeral 43 represents anAF.AE portion formed in the black box 17 and 44 represents a printedcircuit board.

As shown in FIGS. 14A, 14B and 14C, the lens housing 5 thus constitutedis protracted/retracted in a range from a normal imaging state to thecollapsible state after a successive retraction with respect to theintermediate helicoid 6 adjacent to the black box 7. The above-describeddrawings correspond to the positional relationships between the camlever 38 and the cam surface 39a designated by numerals 1, 2 and 3 shownin FIG. 13. FIG. 14B illustrates the position at which the cam lever 38engages to the front end portion of the cam surface 39a.

The operation of the thus constituted lens housing 5 will be brieflydescribed. When the lens housing 5 is positioned as shown in FIG. 14A,the cam lever 38 is positioned away from the cam surface 39a. At thistime, the barriers 36 and the associated elements are positioned asshown in FIG. 11. That is, the coil springs 41 which urge the barriers36 push the fastening pins 36b in the opening direction and push thefastening claws 35b of the barrier operating ring 35. As a result, aforce to rotate the barrier operating ring 35 acts. However, the urgingforce from the spring 40 is larger, so the barriers 36 maintain itsopened state.

From this state, a lens housing driving system (the electric motor 42)is operated by control means (omitted from illustration), causing thelens housing 5 to commence to collapse. As a result, the cam lever 38gradually comes closer to the cam surface 39a of the barrieropening/closing cam 39 until they come in contact with each other andengage to each other. FIGS. 14B and 13 2 respectively show thepositional relationship in this state. The further collapse of the lenshousing 5 causes the cam lever 38 to move along the cam surface 39a. Asa result, the cam lever 38 is, against the urging force of the spring40, rotated upon receipt of the force applied in the rotationaldirection. When the degree of the rotation increases, the urging forceof the spring 40 is enlarged. As a result, the rotation is then stoppedby control means (omitted from illustration) in the final collapse stateshown in FIGS. 14C and 13 3.

The operation of the barriers 36 due to the action of the cam lever 38will be described with reference to FIGS. 11 and 12. When the barrieroperating ring 35 is rotated due to the engagement of the cam lever 38to the cam surface 39a, the fastening claws 35b move in the clockwisedirection, that is, in the direction in which they separate from thefastening pins 36b. In this state, the urging force from the coilsprings 41 acts on the fastening pins 36b. Therefore, the fastening pins36b move while following the fastening claws 35b. As a result, thebarriers 36 are rotated in the closing direction. When the barriers 36are coupled to each other and the closed state as shown in FIG. 12 isrealized, the above-described movement is stopped. On the other hand,the barrier operating ring 35 further rotates by a predetermined angulardegree before it stops at the position at which the lens housing 5 iscollapsed.

When the lens housing 5 is protracted from the collapsed state, the camlever 38 moves along the cam surface 39a by the urging force of thespring 40. As a result, the barrier operating ring 35 is rotatedcounterclockwise when viewed in the drawing, causing the fastening claws35b to be engaged to the fastening pins 36b. The urging force of thecoil springs 41 are overcome, causing the barriers 36 to be rotated inthe opening direction. Then, the rotation is stopped by the front endcylinder portion 5c of the lens housing 5. This state is designated bythe positional relationship shown in FIGS. 11 and 13 2. The lens housing5 is further protracted until its reaches the position shown in FIG.14A.

The present invention is characterized by the thus constituted barrieropening/closing mechanism arranged in such a manner that the cam surface39a of the barrier opening/closing cam 39b adjacent to the lens housing5 which engages to the cam lever 38 for opening/closing the lensprotection barriers 36 on the front surface of the imaging lens inaccordance with the movement of the cam lever 38 in the optical axis ofthe lens is, as shown in FIGS. 13, 15A and 15B, arranged in such amanner that the inclination angle θ2 is enlarged in the range in whichthe urging force of the spring 40 which urges the cam lever 38 in thedirection in which the barriers 36 are opened is large. Furthermore, theinclination angle θ1 (<θ2) is reduced in the range in which theabove-described urging force is small. The above-described angleenlargement/reduction is realized by the urging force of the spring 40.According to this embodiment, a structure is shown in which the camsurface 39a is composed of curved surface formed by continuouslycombining curves having different curvatures.

According to the above-described structure, in the range in which theurging force of the spring 40 acting on the cam lever 38 is large, theinclination angle θ2 becomes enlarged in the portion in which thebarrier opening/closing cam 39 engages to the cam surface 39a.Therefore, the load at the time of rectilinearly moving the lens housing5 can be reduced. Furthermore, in the range in which the urging force ofthe spring 40 is small, the inclination angle θ1 is small in theabove-described engagement portion. Therefore, the load acting on thelens housing 5 can be made substantially the same as that in theabove-described case. As a result, a substantially constant load is ableto act on the driving system for rectilinearly moving the lens housing 5regardless of the magnitude of the urging force of the spring 40 whichacts on the cam lever 38.

The above-described effect will be described in detail with reference toFIGS. 15A and 15B. As shown in FIG. 15A, force F1 acts on the contactpoint at which the cam lever 38 engages to the front end of the camsurface 39a, the force F1 acting due to the driving force of the lenshousing 5, the urging force from the spring 40 and the frictional force.The force F1 actually acts as load Fa for the lens housing 5 and forceFb which moves the cam lever 38. However, since the magnitude of theurging force of the spring 40 is not considerably large in this state,the cam lever can be easily moved even if the inclination (θ1) of thecam surface 39a and the force Fb are reduced. When collapse commencesfrom the above-described state and the state shown in FIG. 15B isrealized, the urging force of the spring 40 becomes enlarged, and forceF2 (>F1) acting on the contact point becomes considerably large.However, load Fc (component force in the direction of collapse) of thelens housing 5 can be reduced in this state since the inclination (θ2)of the cam surface 39a has been enlarged. As a result, the load Fc canbe made substantially the same as the load Fa shown in FIG. 15A. In thisstate, force Fd for operating the cam lever 38 has been enlarged so asto overcome the urging force of the spring 40.

The conventional structure in which the cam surface of the barrieropening/closing cam 39 is a simple slanted surface (reference numeral39c) will be briefly described with reference to FIGS. 16, 17A and 17B.During the opening/closing operation of the barriers 36, force P1 acts,due to the driving force of the lens housing, the urging force from thespring 40 and the frictional force, on the contact point at which thecam lever 38 engages to the front end portion of the cam surface 39c.The force P1 actually acts as load Pa of the lens housing 5 and force Pbfor operating the cam lever 38. In this state, the quantity ofdeflection of the spring 40 is not large and the urging force from thesame is small. When a state shown in FIG. 17B is realized, the quantityof the deflection of the spring 40 becomes large, causing its urgingforce to be enlarged. Therefore, the force P2 (>P1) acts as force Pc(>Pa) of the load of the lens housing 5 and force Pd for operating thecam lever 40. Therefore, the undesirable change in the load that takesplace in the opening/closing operation of the barriers 36 cannot beprevented. According to the thus constituted conventional structure, thelens housing 5 cannot be moved smoothly. Furthermore, in order to drivethe lens housing 5, the driving system including the electric motor 42must be constituted in such a manner as to provide a force of a levelwhich can operate it on the basis of the maximum load state shown inFIG. 17B. Therefore, the motor 42 and the like must have a largecapacity, causing a problem to arise in that a battery will be quicklyconsumed. Therefore, the effect of the invention can be easilyunderstood.

That is, according to the present invention, the structure isconstituted in such a manner that the shape of the cam surface 39a ofthe barrier opening/closing cam 39 is structured as described above.Therefore, the loads Fa and Fc generated due to the engagement of thecam lever 38 to the cam surface 39a can be made uniform and constantover to the entire range of the engagement regardless of the magnitudeof the urging force of the spring 40 acting on the cam lever 38.Therefore, the rectilinear movement of the lens housing 5 by the lenshousing driving system can be made a smooth operation. Furthermore, thegeneration of vibrations and noise due to the load change that takesplace in the above-described lens housing driving system and a mechanismfor opening/closing the barriers 36 in synchronization with the lenshousing driving system can be prevented. In addition, eccentric wear orthe like can be prevented, causing the durability of the overallapparatus to be improved.

The present invention is not limited to the above-described embodiments.The shape and structure and the like of the elements of the cameraincluding the lens housing 5 may be optionally varied/modified. Forexample, according to the above-described embodiments, the cam surface39a is formed by a curved surface having an inclination obtained fromthe relationship with the urging force of the spring 40. However, thepresent invention is not limited to this. For example, a warped surface,a circular arc surface, a parabolic surface or a surface formed byconnecting straight lines may, of course, be optionally employed.

As described above, in the barrier opening/closing mechanism accordingto this embodiment, the cam surface of the barrier opening/ closing camadjacent to the camera housing is arranged as follows: the barrieropening/closing cam being arranged to engage to the cam lever, whichopens/closes the lens protection barrier disposed on the front surfaceof the imaging lens, so as to open/close the barrier in accordance withthe movement of the cam lever in the direction of the optical axis ofthe lens. The cam surface is arranged in accordance with the urgingforce of the spring in such a manner that the inclination angle isenlarged in a range in which the urging force of the spring for urgingthe cam lever in the direction in which the barrier is opened is large.Furthermore, the inclination angle is reduced in a range in which theurging force is small. Therefore, the load of the cam lever due to theengagement of the barrier opening/closing cam to the cam surface can besubstantially uniform over the entire range of the above-describedengagement regardless of the magnitude of the urging force of the springacting on the cam lever. Therefore, the lens housing can be smoothlyrectilinearly moved by the lens housing driving system. Furthermore, thegeneration of vibrations and noise due to the load change that takesplace in the above-described lens housing driving system and a mechanismfor opening/closing the barriers 36 in synchronization with the lenshousing driving system can be prevented. In addition, eccentric wear orthe like can be prevented, causing the durability of the overallapparatus to be improved.

Although the invention has been described in its preferred forms with acertain degree of particularly, it is understood that the presentdisclosure of the preferred forms may be changed in the details ofconstruction and the combination and arrangement of parts withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:
 1. A camera having a camera housing and comprising:alens protection barrier member for covering an imaging lens; a camlever, connected to said barrier member, movable along an optical axisof said imaging lens, and rotatable around said optical axis duringopening/closing of said barrier member; a variable force spring member,connected to said cam lever, urging said cam lever to rotate in adirection in which said barrier member opens; and a cam fixed to saidcamera housing on a path on which said cam lever moves along saidoptical axis and having a cam surface engagable with said cam lever bymovement of said cam lever along said optical axis; said cam lever beingurged against said cam surface by said spring force and moving alongsaid cam surface while rotating during opening/closing of said barriermember, the shape of said cam surface being correlated with the force ofsaid spring member so as to vary a load force exerted by said cam leverin order to maintain said load force substantially constant as saidforce of said spring member varies.